1. Field of the Invention
This invention relates to a method of manufacturing a guidewire with an extrusion jacket, and more particularly, to a method of manufacturing a discrete length guidewire of varying thickness. The invention also relates to a method of manufacturing a discrete length guidewire with a helical stripe on the extrusion jacket.
2. Description of the Related Art
Medical guidewires are generally used for navigating through internal passageways of a body. A typical guidewire includes a corewire having a proximal shaft of constant diameter and a taper section of progressively narrowing diameter leading to a distal tip. In order to prevent damage to the body, the guidewire typically includes a relatively soft plastic jacket on the outer surface. The distal end of a guidewire is introduced into a body by a physician through an opening in the body. The physician manipulates the tip of the guidewire through the body to a site to be treated. A catheter or other medical device is usually advanced over the guidewire to the treatment site, and the guidewire is then removed.
Current methods of manufacturing a guidewire with an extrusion jacket have certain drawbacks. Current methods utilize a continuous spool of corewire during the tapering of sections into the corewire, as well as during the extrusion of a plastic jacket onto the corewire. The use of a continuous spool of corewire during tapering and for extruding a jacket onto the corewire is complex and cumbersome. It is difficult to grind a continuous spool of corewire with a varying tapered diameter.
One method of producing a spool of continuous corewires involves the use of acid to etch a taper onto the corewire. The etching method, however, raises environmental concerns. Therefore, for the above reasons, the current methods for manufacturing a continuous tapered corewire are less than desirable.
After the continuous spool of corewire is manufactured and ground, a plastic jacket is typically applied to the outside surface of the corewire. The current methods utilized in applying a plastic jacket to a continuous spool of corewire have certain drawbacks. A typical method of jacketing a continuous corewire also uses a pay-off spool and take-up spool. In this method, the corewire unwinds from a pay-off spool and is then led through a crosshead with a jacket extruder. As the corewire passes through the crosshead, a jacket is extruded onto the corewire. The jacket is then cooled, and the wire is either respooled onto a take-up spool or cut to a predetermined length. After the corewire is cooled, therefore, additional steps, such as cutting the corewire to a length, are required in order to obtain a usable discrete length guidewire. There is a need therefore for a method of extruding a jacket on a corewire which substantially obviates these drawbacks.
Some jackets of conventional guidewires include a helical stripe to make it easier for a surgeon to see that the guidewire is being longitudinally displaced in the opening of the human body. The current method for applying a jacket having a helical stripe to a corewire also has certain drawbacks. In order to obtain a guidewire with a helical stripe, a heat shrinkable hollow tube is used. The heat shrinkable tubing is manufactured by extruding a longitudinal stripe on the hollow tube and then heating, twisting, and cooling the hollow tube. This heat shrinkable tubing can then be heat shrunk onto a corewire to form the jacket of the corewire. This process of heat shrinking the tubing on a corewire, however, does not provide a very strong connection between the jacket and the corewire. Therefore, this can result in a guidewire in which undesired movement occurs between the corewire and the jacket. Moreover, only a limited number of materials are suitable for heat shrinkable tubing, thereby limiting the type of materials that can be used for the jacket. There is a need therefore for a method of manufacturing a guidewire with a jacket having a helical stripe which substantially obviates these problems.